<script src="vue.js"></script>

<div id="app">
    <input type="text" v-focus="true" />
</div>

<script>
    Vue.directive('focus', {
        inserted(el, binding) {
            if (binding.value) {
                el.focus()
            }
        }
    });
     
    var vue = new Vue({
        el: "#app",
    })
</script>